1. Field of the Invention
The present invention relates to laser mirrors and, more particularly, to a liquid or gas cooled cylindrical mirror for a high powered laser.
2. Description of the Prior Art
Metallic mirrors are commonly used to focus, deflect or change the shape of laser beams. A problem associated with the use of such metallic reflectors is the absorption of incident beam energy by the mirror surface and the resulting thermal distortion of the optical reflective surface. Typically, the mirrors which are subjected to intense heat by the laser beam require cooling of the reflective surface since only minimal thermal distortion due to differential temperatures can be permitted. Examples of liquid-cooled mirrors include U.S. Pat. No. 4,143,946 to Leo et al, and U.S. Pat. No. 3,836,236 to Kirk et al. Kirk et al discloses a cooling means in the form of an elongated cooling passage, which is located in the central part of the backing plate of a mirror, and a mirror mounting means which includes an outer mounting ring having an inwardly projecting annular lip defining a shoulder for receiving and positioning a disc-like mirror. Leo et al discloses a cooled deformable laser mirror which uses an inlet manifold and a plurality of spraying nozzles for cooling the rear surface of the mirror. In addition, Leo et al discloses the use of electro-magnetic actuators which are used to exert a force on the rear surface of the mirror to thereby modify the geometry thereof.
A disadvantage of the fluid cooled laser mirrors of the prior art is that separate means have to be provided for cooling the mirror and for adjusting its curvature. This disadvantage is obviated by the system of the present invention whereby vertically adjustable cooling conduits may be used both to effect heat transfer away from the mirror surface and to adjust the mirror geometry to compensate for the fading effect at the outer edges of a laser beam.
Further examples of prior art which deal with the cooling and curvature control of an optical reflecting surface are U.S. Pat. No. 4,059,346 to Lavine et al, U.S. Pat. No. 4,003,640 to Hanson, U.S. Pat. No. 3,664,020 to Shannon, U.S. Pat. No. 4,110,013 to Eitel and the article "Cylindrical Mirror with a Controlled Radius of Curvature", by Yu. A. Ananev and Ve Sherstobitov, appearing in Soviet Journal of Quantum Electronics, Vol. 4, No. 12, June 1975.